File Comparision byte by byte

Can anyone tell me how to compare two files in C byte by byte

fopen both, fgetc both in a loop. You might also consider using ==. But really you can do this with any function that reads from a file.


Quzah.

is there a function called bcompare,if there is,how do i use it.Is it easier than fopen and fgetc?

Quote:

---

Originally Posted by anusha2489

is there a function called bcompare,if there is,how do i use it.Is it easier than fopen and fgetc?

---

In the time it took you to type this, you could have just googled 'bcompare' to see if there was in fact a function called 'bcompare', and if so, how you would use it.


Quzah.

Quote:

---

Originally Posted by quzah

In the time it took you to type this, you could have just googled 'bcompare' to see if there was in fact a function called 'bcompare', and if so, how you would use it.
Quzah.

---

Alternatively, if he has the help documentation for his compiler (most come with it) done the search in about half that time.

I am actually trying to write a peer-peer program, where I need to compare the peerids that a peer send with the peer ids that I have and add those that I do not have. Peerid is struct with port and ip.
How do i do this

Quote:

---

Originally Posted by anusha2489

I am actually trying to write a peer-peer program, where I need to compare the peerids that a peer send with the peer ids that I have and add those that I do not have. Peerid is struct with port and ip.
How do i do this

---

Well, the first thing you need to do is decide which project you're writing... are you comparing files or comparing IP addresses?

Take my word for this... if you give us wrong information you will get wrong answers.

I need compare IP addresses and port no.s

The peer id is IP+Port no.

Quote:

---

Originally Posted by anusha2489

I need compare IP addresses and port no.s

The peer id is IP+Port no.

---

Ok for that you can use the already defined SOCKADDR_IN structure which is filled in by recvfrom() in the sockets library.

Just store a list of already received structs in an array (sorting is optional depending how many you have). Then compare...

Code:

---

if (thisaddr != thataddr)
  storethisaddr(thisaddr);

---

C will let you compare structs.

> C will let you compare structs.
Are you sure?

Code:

---

$ cat bar.c
struct foo { int bar ;};
int main ( ) {
  struct foo a, b;
  if ( a == b );
  return 0;
}
$ gcc bar.c
bar.c: In function ‘main’:
bar.c:4: error: invalid operands to binary == (have ‘struct foo’ and ‘struct foo’)

---

If you want to compare a struct, you need to use == (or strcmp, or memcmp) for each member of the structure.


> I am actually trying to write a peer-peer program,
If you're still struggling with comparisons, then I would suggest you practice C some more, before trying to write an actual program.

Quote:

---

Originally Posted by Salem

> C will let you compare structs.
Are you sure?
If you want to compare a struct, you need to use == (or strcmp, or memcmp) for each member of the structure.

---

OOPs... I'm thinking some Pascal leaked in there somehow... yes, memcmp() works... my bad.

(and yes, that still happens sometimes... I'll be working on something and here's this whole chain of a := b; stuff....)

> yes, memcmp() works... my bad.
Do you want to try again?

memcmp() does not work on two structs, because you have no control over what data lies in all the slack/padding bytes between members.

You have to compare each member, with whatever makes most sense for each member.

Quote:

---

Originally Posted by Salem

> yes, memcmp() works... my bad.
Do you want to try again?

memcmp() does not work on two structs, because you have no control over what data lies in all the slack/padding bytes between members.

You have to compare each member, with whatever makes most sense for each member.

---

Ok... would you believe... Chuck Norris with a BB gun?

Hmmmm... you're right again...